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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.nio.channels;

import java.io.IOException;
import java.nio.ByteBuffer;


/**
 * A channel that can read bytes into a sequence of buffers.
 *
 * <p> A <i>scattering</i> read operation reads, in a single invocation, a
 * sequence of bytes into one or more of a given sequence of buffers.
 * Scattering reads are often useful when implementing network protocols or
 * file formats that, for example, group data into segments consisting of one
 * or more fixed-length headers followed by a variable-length body.  Similar
 * <i>gathering</i> write operations are defined in the {@link
 * GatheringByteChannel} interface.  </p>
 *
 * @author Mark Reinhold
 * @author JSR-51 Expert Group
 * @since 1.4
 */

public interface ScatteringByteChannel
    extends ReadableByteChannel {

  /**
   * Reads a sequence of bytes from this channel into a subsequence of the
   * given buffers.
   *
   * <p> An invocation of this method attempts to read up to <i>r</i> bytes
   * from this channel, where <i>r</i> is the total number of bytes remaining
   * the specified subsequence of the given buffer array, that is,
   *
   * <blockquote><pre>
   * dsts[offset].remaining()
   *     + dsts[offset+1].remaining()
   *     + ... + dsts[offset+length-1].remaining()</pre></blockquote>
   *
   * at the moment that this method is invoked.
   *
   * <p> Suppose that a byte sequence of length <i>n</i> is read, where
   * <tt>0</tt>&nbsp;<tt>&lt;=</tt>&nbsp;<i>n</i>&nbsp;<tt>&lt;=</tt>&nbsp;<i>r</i>.
   * Up to the first <tt>dsts[offset].remaining()</tt> bytes of this sequence
   * are transferred into buffer <tt>dsts[offset]</tt>, up to the next
   * <tt>dsts[offset+1].remaining()</tt> bytes are transferred into buffer
   * <tt>dsts[offset+1]</tt>, and so forth, until the entire byte sequence
   * is transferred into the given buffers.  As many bytes as possible are
   * transferred into each buffer, hence the final position of each updated
   * buffer, except the last updated buffer, is guaranteed to be equal to
   * that buffer's limit.
   *
   * <p> This method may be invoked at any time.  If another thread has
   * already initiated a read operation upon this channel, however, then an
   * invocation of this method will block until the first operation is
   * complete. </p>
   *
   * @param dsts The buffers into which bytes are to be transferred
   * @param offset The offset within the buffer array of the first buffer into which bytes are to be
   * transferred; must be non-negative and no larger than <tt>dsts.length</tt>
   * @param length The maximum number of buffers to be accessed; must be non-negative and no larger
   * than <tt>dsts.length</tt>&nbsp;-&nbsp;<tt>offset</tt>
   * @return The number of bytes read, possibly zero, or <tt>-1</tt> if the channel has reached
   * end-of-stream
   * @throws IndexOutOfBoundsException If the preconditions on the <tt>offset</tt> and
   * <tt>length</tt> parameters do not hold
   * @throws NonReadableChannelException If this channel was not opened for reading
   * @throws ClosedChannelException If this channel is closed
   * @throws AsynchronousCloseException If another thread closes this channel while the read
   * operation is in progress
   * @throws ClosedByInterruptException If another thread interrupts the current thread while the
   * read operation is in progress, thereby closing the channel and setting the current thread's
   * interrupt status
   * @throws IOException If some other I/O error occurs
   */
  public long read(ByteBuffer[] dsts, int offset, int length)
      throws IOException;

  /**
   * Reads a sequence of bytes from this channel into the given buffers.
   *
   * <p> An invocation of this method of the form <tt>c.read(dsts)</tt>
   * behaves in exactly the same manner as the invocation
   *
   * <blockquote><pre>
   * c.read(dsts, 0, dsts.length);</pre></blockquote>
   *
   * @param dsts The buffers into which bytes are to be transferred
   * @return The number of bytes read, possibly zero, or <tt>-1</tt> if the channel has reached
   * end-of-stream
   * @throws NonReadableChannelException If this channel was not opened for reading
   * @throws ClosedChannelException If this channel is closed
   * @throws AsynchronousCloseException If another thread closes this channel while the read
   * operation is in progress
   * @throws ClosedByInterruptException If another thread interrupts the current thread while the
   * read operation is in progress, thereby closing the channel and setting the current thread's
   * interrupt status
   * @throws IOException If some other I/O error occurs
   */
  public long read(ByteBuffer[] dsts) throws IOException;

}
